I will be arguing for Pro on this one. I had a debate like this in the past on my other account, and I won. I feel I can win again, versing my opponent. 4 rounds, because this is a minor debate to me, I have a major debate going on as well. 9,000 characters. 72 hours to argue.

DEFINITIONS:

These definitions are not to change at all throughout the debate, if you want to change it, message me. Both sides will use this.

Sentient: responsive to or conscious of sense impressions. [1] In other words, self-aware.

Animal: one of the lower animals as distinguished from human beings. [2]

Animals do not seem to be self aware. Higher cognitive abilities are only the result of this. Their cognitive ability is far too low to comprehend their own existence. Wile they may have a visual perspective, they would not be "self aware" in the way that they can distinguish themselves clearly from their environment in an interpretive sense. They would respond to stimuli, but as merely an instinctual result. The only animals I could see possessing this capability are apes, dolphins, elephants and intelligent dogs. Specifically chimpanzees with their neo-cortex and other advanced brain composition features. I will be arguing that sentience derives solely from cognitive ability and only highly evolved animals can begin to posses this ability of the mind.

I would like to thank my opponent for accepting my debate. Should be a good one!

ARGUMENTS:

I would like to focus on this definition of sentient.

"responsive to or conscious of sense impressions."

Basically what this means is being able to perceive/display feelings, or being self-aware.

DEFINITION OF SELF-AWARENESS:

an awareness of one's own personality or individuality. [1]

Now, lets take it back to sentient. Able to display feelings.. I go to my cat and pet her. This is what she looks like. (http://www.womansday.com...) She also starts purring, which is a sign of happiness among cats. Well, happiness is a feeling/emotion, isn't it? As a matter of fact, it even looks like her face is smiling. How about dogs? I pet a dog, it looks like this (http://www.thedogtrainingsecret.com...) Another smile. I can do this with any other animal, and I bet you I will find a smile. This proves that in fact, animals are sentient. Animals are showing happiness.

Another self-awareness factor is knowing that you exist. A way to prove this is something called "The mirror test." This "mirror test" is a test, where they put a 80 inch mirror in a room with another animal, to see how it will act with it's own reflection. If the animal does ANYTHING to the mirror (for example, attack it, bark at it, or threaten it) they fail. The objective is to see if they know it is themselves in the mirror. MANY animals have passed it, including bonobos, chimpanzees, gorillas, killer whales, dolphins, even elephants. This can prove that animals are self-aware because they can see themselves in the mirror, and recognize it is them, and not another animal. [2]

The brain of the animals are not so different from human's, some are smaller, some are bigger, but they all basically have the same shape. They also have most of the same parts that human's have, so shouldn't they have no problem doing what human's do, which is being self-aware? [3]

Brain to size mass can also determine self-awareness, and in fact, humans do not have the biggest brain to body mass ratio. This basically shows the intelligence of certain animals. The higher the ratio, the more intelligence the animal has, in theory. Notice my opponent said I have to prove that ants are sentient too, well, they have the biggest ratio in the list! [4]

As you can see, humans are actually 5th on the list. And one of these animals are not that bigger than a human. The lion. As a matter of fact, a lion's average height is only 120 cm, which is only 3 feet 11 inches(at shoulder) [5]. If they were on their hind legs, they would be about 7 feet. Some humans are this tall, for example, Yao Ming, who is even taller than this, is 7 foot 6. [6] Not to mention a horse is on here, which is slightly bigger than a lion.

I have found a couple misconceptions in your arguments and would like to explain

First things first, I never argued that all animals are not sentient, just arguing that for sure many animals are not.

I accepted from the beginning that your cat, dog and other animals with displayed cognitive development are sentient, but to say all animals are is a fallacy, which I will discus later on

The fact that your clarification in the comments says "All animals. And no, I've seen people who do not believe animals are sentient." shows me already that some animals, by your definition, lack sentience.

For example, the animals in the mirror who DO bark or attack etc. By saying 'many' have passed, you are indirectly saying that some have definitely failed, which you can thus clearly disproving the fact that all Animals display sentience.

Another I found is that you say that "The higher the ratio, the more intelligence the animal has"

This can be clearly disproved due to the fact that Neanderthals had larger brains per say than humans, but the capacity filling it was primarily for senses such as sight, smell, etc. Their actual lobes responsible for logical, creative, and analytically thinking however were significantly inferior of that of the humans.

So we can see that although brain size to mass ratio is a good start, it is for sure not the only indicator

My main argument however, is how we are defining "Animal"

From google-

"an"i"mal
G2;anəməl/Submit
noun
1.
a living organism that feeds on organic matter, typically having specialized sense organs and nervous system and able to respond rapidly to stimuli.

So this raises many questions for me. How about a Jellyfish? They don't have a brain that can think, only a cluster of nerves that can in no way develop self awareness. They are purely chemicals that respond to their environment. Starfish? Sponges? Clams? Zooplankton? Coral? All are animals, yet they definitely have no self awareness
Even though common Insects have brains, but similar to the Neanderthals it is all used for sensory information of the surroundings.